3.3.4 Encasement of the Charters of Freedom

Mark Vangel, Mark Levenson
Statistical Engineering Division, ITL

Charles Tilford
Process Measurements Division, CSTL

In the early 1950's, the predecessor of NIST, the National Bureau of Standards, played a leading role in the creation of cases for the protection and viewing of the Charters of Freedom, which include, The Declaration of Independence, The Constitution, and The Bill of Rights. Now after nearly 50 years, the cases require replacing. NIST is again playing a leading role in the design and manufacturing of the new cases. The cases will meet optimal viewing and protection requirements, including the ability to access the documents and to monitor and service the cases. Scientists and engineers throughout NIST are providing expertise on the project. The accompanying figure displays a cut-away view of the proposed cases. Statisticians have been asked to develop a data analysis model based on environment measurements to detect any leakage of harmful atmospheric gases into the case.

The equation below relates the environment measurements, such as pressure, temperature, water partial pressure, and certain constants to the rate of leakage, L_m.

$$P_i = P_0[1 + (1/T_0 +W)(T_i - T_0) + K(P_i-Q_i) + L_mt_i + C_v\sum_{k=1}^i(P_k-Q_k)\Delta t_k]$$

The measurements, which have uncertainty associated with them, will be made at discrete time periods. Based on the physical model described by the equation and considerations of uncertainty, a mathematical rule will be derived to signal the existence of a possible leakage.

Figure 13: Cut-away view of the proposed cases.

       

Date created: 7/20/2001
Last updated: 7/20/2001
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